I like customization. Most mecha systems I've played are at two extremes though. Either you can't customize by RAW at all, like with Robotech, or you can customize super hard but there is a mountain of constant maths you need to do to balance power output and heat and weight...

Like, you want to armor your mech up but that adds weight, so you need more power for it which creates heat issues... it's mentally taxing to work through and any changes you make during gameplay require that same mass of maths. I'd enjoy something somewhere in the middle between extreme bookwork and entirely pre-fab.

I like the melodrama. Young people (not necessarily high school students, but still young people) in high stress situations trying to balance the rigidity of military life and discipline with the rock star adulation you can get by saying "yeah babe, I'm a mech pilot." It creates a cocktail of emotions that lead to some really fun interactions if played right.

I like the settings mecha bring with them. A world has to have some reason that giant fighting robots are the primary machines of war, and they're usually cool or wacky in the best ways. Sometimes both. To give specific examples, I'm a fan of G Gundam and Xenogears. I didn't finish Macross Delta, but I also thought the concept was rather fun.

Ditto on the melodrama, in case that wasn't clear by the shows and game I mentioned. : )

The wackiest mecha anime that (probably) took itself entirely seriously was Valvrave, where you have a high school declare itself an independent nation and fight a war in space with mechs while becoming immortal space vampires.

I'm a big fan of the mecha genre in general. Some of my favorite games were Xenogears and Zone of the Enders. While some of my all-time favorite mecha anime include Gurren Lagann, Robotech, Vandread, Macross Frontier (Delta ended up as a guilty pleasure, but not particularly great), NGE (especially the remake), and the various Gundams. Even got into the manga of

Isekai about a programmer reborn in a magic world with giant robots - goes crazy about said giant robots and is determined to build and pilot one of his own design. Is a haxx mage because he known how to program like a boss.

One of the big things about mecha that I enjoy is the mecha designs. I've never found an RPG system that captures the level of complexity I'd like (Mekton is too much, but most others are just too light) Lancer is kinda close, but I feel like it needs just a bit more in the grander scheme.

A while back, I considered making a hack of Shadowrun 5e for a mecha game, since I found the core system to be robust enough, but obviously would need a lot of work to make it right for a mecha system. Haven't started, but I pondered heavily about it LOL

I'm a big fan of the mecha genre in general. Some of my favorite games were Xenogears and Zone of the Enders. While some of my all-time favorite mecha anime include Gurren Lagann, Robotech, Vandread, Macross Frontier (Delta ended up as a guilty pleasure, but not particularly great), NGE (especially the remake), and the various Gundams. Even got into the manga of

Isekai about a programmer reborn in a magic world with giant robots - goes crazy about said giant robots and is determined to build and pilot one of his own design. Is a haxx mage because he known how to program like a boss.

knight and magic got anime too and i think it was one of the best isekai shows i recently watched

For me it is also customization. In macross series we see many different types from same fighter. ın gundam there are usually different types i especially like wing, seed and 00 for that but another reason is pilots feel dinstinct enough to be a rpg party especially in wing and 00.